Legal requirements when collecting personal data (e.g. passport id)

I am developing form for a company dealing with visa, receiving such data as passport number or other personal info is crucial. Are there any laws, regarding the way how it should be collected? I know there are laws (or policies) regarding storage of personal data, but what about case when I want to ask user to fill in form and results will NOT be storted in databases, instead will be sent to email? Should I use https connection, should I use any encription or it is up to me? Any help will be appriciated))